The Ames M500 is a reduced pressure detector assembly (RPDA). It is available in 2 1/2″-10″ sizes and has been in production since 2000. The body is made of stainless steel. The M500 has used multiple devices for the bypass assembly. It currently utilizes a 3/4″ 919 for the bypass assembly. A lead free version (LFM500) was introduced in 2013.